They would probably charge you a cancellation fee for the first reservation and then you could rebook at the deluxe and pay the new resort reservation and they'd credit you back for your first one in 2 weeks?
I know that we had a situation similar to this, but not Disney. We'd book a pool house, with a jacuzzi tub and when we arrived they sent us to this little 20 year old house with no pool (unless you consider the septic leak in the back yard from the next door trailer park), and no jacuzzi. The house was unclean, and not what we'd paid for. So I called, and they said to come back to the main office and they'd fix it. We drove all the way back to the main office and they said they had no more availability but would credit us the difference for lack of pool and lack of jacuzzi. I said no, that those were not the only problems and so they said they'd issue a credit, but it could be up to 2 weeks for the charges to show back up on our card.
We were put out finding a hotel in Orlando at the last second, but we did and it all worked out.
I'd just call the main reservations number and ask.....maybe they do it differently at Disney. I mean they give people free upgrades all the time when they overbook the hotels, so maybe it's treated the same and the new ressie is just moved over and you can pay the difference as long as their is availability. They may charge you that change fee though?